Did it happen recently, or has it been like this since you started downloading? Does some CC show up, or none at all? And have there been any changes in your game recently, like a new EP or SP?
In any case, I think the two links I gave you should cover most CC troubles. I suggest you go through link #2, and follow the steps.
When I started downloading, everything was fine. Then some hairs didn't show up, even though the mesh was there. Now some outfits aren't showing up even though the meshes are there. The thing is, me and my sister share the same computer, but we don't share the same Sim game(she has one on her side, I have one on mine) The hairs that won't show up in my game show up in hers. Most CC shows up unless I don't have the mesh, but I knew those didn't have the mesh, and are looking for them
I haven't gotten any new EP's or SP's. My EP goes up to OFB, i'm mainly getting the box sets when they come out (haven't got fun with pets yet)